Minor Issues calibrationg the Printer

this is my first Project runing Reprap Firmware and the duet3d controller board. before that i was using Marlin and Repertier FIrmeware.
First of all iam very fascinated of the Duet3d because of all of the possibilitys you can do with it.
Iam using the Duet WIfi and the Duex5 because iam running on 8 Motors. Iam Using the automatic bed Leveling with 3 independent Motors and the Precision Piezo as a trigger.
Iam also using two Extruder and two Motors for die X-Axis and one for die Y-Axis. all of that works prety good and my results looks pretty good too, instead of the corners..

Iam Using a Bowden Setup with an E3D Titan extruder. The bowden length is 800mm wich means i need a lot oif retraction and a lot of retraction speed so i saw the pressure advance article on the Doku site and tried to configure it.. but when i use the pressure advance my extruder is starting to make a wierd mechanical noise, not like fiolament grinding it sounds really mechanic… and that with an S value of 0.1.. maybe there is an Failure and you can help me..

i cant quite see a difference with or without the pressure advance.. I thing those blobs happen between a layer change. so it seems like there is to much pressure in the bowden system..

the other thing that i have problems with is the Precision piezo.. i cannot configure it.. it is so sensitiv that even if i pet my case really slightly it triggers.. i checked the polarisation and turned on the screw but nothing happens is there any opportunity to configure the sensitivity in the config.g file ?